Well, you all convinced me to try it, so - after measuring the pan I use the most, I bid on, and won, a somewhat-classic Griswold pan with about the same bottom-area.
This one has been cooked on, and most of the center of the pan felt pretty slick. Thing is, while the pan was/is black, it's not a horror-story of crud and/or rust... in fact, it looked just like I would expect a cast-iron pan to look after I had used it for a good while. Now I'm both a bit adventurous, and a bit conservative... and a few other things... but I don't see the need to bake this thing in a self-cleaning oven, use soap and water or anything that would cause me to have to go through the myriad of steps just to re-season it again. I mean, I guess some people feel better about getting a new-to-them used cast-iron pan totally clean, as if it's a fresh start on a sanitary surface, but I don't have quite as many hold-ups about food (I've worked in restaurant kitchens when I was younger, and I think the image of the cast-iron pan on the horse's tail-end for a dusty, dirty trail ride that Paul put up here: http://www.richsoil.com/cast-iron.jsp
speaks plenty about what can be eaten on without causing ten different plagues).
At least i hope it does.
Anyway, I went with boiling water in it for a bit, then placing a mix of some olive oil (I know, I read not to cook with olive oil... but it's here and it's handy) and the fat off of bacon in it to re-coat the surfaces while the pan was still hot. I sorta used the oils/fats and multiple bunched-up paper-towels to "polish" the surface over and over to help bring up more of the older cooking stains, but the paper-towel was the most abrasive thing I used in it.
So am I taking too many chances here, or do some of you buy old cast-iron cookware without knowing the owner and just pretty much get right to using it (instead of the in-depth cleaning so many cast-iron topics seem to get into)?
As an aside, I believe I have that ideal polymerized coating on the bottom of the aluminum/teflon pan I am finally done using (no, not the cooking-surface bottom... I mean the bottom that sits on the burner). I didn't realize what it was, but knew it was hard and slick... much slicker than what the outside-aluminum started out to be. It never hit me that, hey, that's an ideal cooking surface, and what I'd be aiming for with a cast-iron pan. I think it was from the layers of bacon-grease that would drip down a little after I poured out excess grease each time I cooked bacon.